The present invention pertains to forage harvesters of the type adapted to move over the crop and harvest it, chop the crop material and then blow it into a receptacle such as a trailing wagon. In devices of this character certain problems arise due to the gumming up of the crop material along its path through the harvester, sometimes to such an extent that this gumming up retards or prohibits the free flow of material through the harvester. This gumming problem may occur in various portions of the harvester, such as in the portions which transfer the crop material from one of the elements or the other. This gumming often stops the free flow and it is desirable to be able to keep the various conveying areas of the harvester in a "slick" condition for maximum efficiency in moving the cut material through the harvester. This gumming up can thus occur in various parts of the harvester, depending on the type of material being conveyed and/or the condition, particularly the moisture content of it.
Such mobile harvesters are adapted to travel over the field for a considerable period of time in filling a trailing wagon for example, and the amount of water that can be carried by such a harvester is limited. Accordingly, it is necessary to efficiently use the water not only as to the location at which it is discharged into the stream of crop material, but also as to the amount of water discharged as well as being dependent on the amount of material flowing through the machine at any time.